Downdraft carburetor



Sept. 14, 1937. A. H. BLATTNER. ,0

DQWNDRAFT CARBURETOR 7 Filed larch 20. 1933 2 Sheets-Sheet 1 IN VENTOR A TI'ORNEY 'Sept. 14, 1937. A. H. BLATTNER DOWNDRAFT CARBURETOR Filed March 20. 1933 2 Sheets-Sheet m W a H r w w 4 m VENTOR A TTORNE Y UNITED STATES PATENT OFFICE DOWNDRAFT CARBUBETOB- August H. Blattner, St. Louis County, Mo., as-

signor to Carter Carburetor Corporation, St. Louis, Mo., a corporation of Delaware Application March '20,

10 Claims.-

This invention. relates to carburetors and more particularly to downdraft carburetors. The object of the invention is to provide a generally new and improved downdraft carburetor construction, capable of being produced by modern methods such as die casting.

A further object of the invention is to produce a carburetor construction of the downdraft type, constructed in such a manner as to avoid the phenomenon of percolation which is such a well known source of trouble in downdraft carburetors.

Other objects of the invention will appear from the following description and accompanying drawings, referring to which:

Figure 1 is a vertical sectional elevation of a carburetor constructed according to my invention.

Figure 2 is a sectional plan view of the carburetor shown in Figure 1, the section being taken along the line 2-2 in Figure 1.

Figure'3 shows a. plan view of the main venturi constructed according to my invention.

Figure 4 is a vertical sectional view of the main venturi shown in Figure 3.

The reference numeral I indicates the base or attaching flange member of a carburetor, having a flange 2 thereon by means of which it may be attached to the manifold of an internal combustion engine. While the manifold, which is diagrammatically indicated at 35, forms no part of this invention, it will be understood that present practice in the construction of internal combustion engines is to practically combine the intake and exhaust manifolds, at least at certain points, 'for the purpose of heating the fuel mixture, so that the intake manifold and the carburetor above it are subjected to very high temperatures, particularly when the motor is slowed down or stopped after being operatedat highv speed for a substantial period.

The base member of the carburetor including the flange 2 is preferably made of cast iron and carries the throttle valve 3, mounted on shaft' l and controlling the mixing conduit 5. The main venturi 6 is formed as a separate die casting, having a flange l which is mounted between'two heat insulating gaskets 8 and 9 as indicated in Figure 1.

The upper part of the mixing conduit 5 is cut away as indicated at Ill to prevent direct heat transference to the main Venturi member. The upper part of the main venturi is also externally recessed as indicated at l l to minimize the trans-. fer of heat from this memberto the intermediate body member l2 which is formed as a die casting,

preferably of zinc or aluminum. The primary' venturis and the full reservoir or float chamber 1933, Serial No. 661,682

The upper part of the carburetor comprises the member l5 which may be referred to as an air downwardly into the float chamber l3 and having an opening therein to receive the pivot pin [8 of the float IS. The float valve 20 is of conventional construction except that it is mounted in a needle seat 2|, screwed into the same member on which the float itself is pivoted. By this construction the float and float valve may be removed as an assembly when the float chambercover is removed.-

It will be noted that the float chamber [3 is provided with substantially parallel walls 22, (Fig. 2) spaced just far enough apart to receive the float pivot pin l8 and the projection I! so that no retaining devices are required to prevent the disassembly of the pin I8 from the float mechanism.

The fuel is supplied to the float chamber through the inlet connection 24 and maintained substantially at the lever A--A by the float mechanism. The main nozzle [4 is mounted in an inclined position to receive its fuel thru the main metering jet 25, which jet is controlled by a con,- ventional metering rod 26, having a plurality of metering steps one of which is indicated at 21 to variably restrict the jet or nozzle 25 in accordance with the requirements of the carburetor. The metering rod is connected to the rocker arm 28 by means of a loose fitting pin 29 and the rocker arm is operated by any suitable means such as a connection to the throttle or to a suction operated piston. This operating means however, forms no part of this invention and is not shown. It may be stated however, that the rocker arm 28 is mounted on the rock shaft 30, carried in pillow block 3|, and the float bowlvent 32 is carried at a high point in the hollow pillow block to prevent fuel splashing out of the opening. A fuel supply conduit 33 extends upwardly through portions I and I2 of the carburetor body to a point above the fuel level and is connected to the main nozzle by means of conduit 34. A suitable inside vent 35 is provided at the upper end of the conduits The recessed portions Ill and II, together with the heat insulating gaskets 8 and 9 function to resist to a substantial extent the upward trans-- ference of heat from the flange 2 and the manifold to the float chamber l3 and the main nozzle l4. Incase sufficient heat is developed to start a boiling action in the liquid fuel, small bubbles will begin to form in the chamber 36 and the lower part of the main nozzle. The greater part of these bubbles will find their way out thru the conduit 34 and vent 35, thereby dissipating the lower boiling constituents of the gasoline and also 00 resisting the tendency of large bubbles to form and pass up thru the main nozzle M, which would initiate what is known as percolation.

It is well understood that ordinary gasoline is a mixture of a large number of different hydrocarbons. boiling at different temperatures and after the first 10 or has been boiled off, the residue is what is known as weathered gasoline which will not boil under the temperature conditions to which the nozzle l4 and the float chamber l3 are subjected. The provision of the conduit 34 which leads directly upwardly from a point in the upper side of the nozzle I4, together with the provision of the vent 35 at the upper end of conduit 34 .permits the escapeof the lower boiling constituents, leaving weathered gasoline in the chamber 36 and nozzle l4 so that no percolation occurs.

The invention is not limited in details to the structure shown but may be modified in various respects as will occur to those skilled in the art and the exclusive use of all such modifications that come within the scope of the appended claims is contemplated.

I claim:

1. A downdraft carburetor having a base member for attachment to the manifold of an internal combustion engine, a fuel containing member mounted above said base member, a main Venturi member, having an outwardly extendin flange member interposed between said base member and. said fuel containing member,-and.means located both above and below the flange member for interrupting the transfer of heat.

2. In a downdraft carburetor, a base member having a mixing conduit, a main Venturi member having an outwardly extending flange mounted on said base member, said Venturi member having a portion projecting into said mixing conduit, the upper wall, of said mixing conduit and the outer wall of said projecting portion being spaced apart to prevent direct transference of heat, and insulating gaskets mounted above and below said flange.

3. In a downdraft carburetor, a base memberhaving a mixing conduit therein, a main Venturi member having an outwardly extending flange andbeing mounted on said first named member, said Venturi member having a portion pro- 'jecting into said mixing conduit, the upper wall of said mixing conduit and the outer wall of said projecting portion being spaced apart to prevent direct transference of heat, an upper body member mounted above said Venturi member, and heat insulating gaskets separating said Venturi member from said upper and base members.

,4. In a downdraft carburetor having a mixing conduit, a base member having an opening forming the lower part of said mixing conduit, a main Venturi member having an outwardly extending flange and being mounted on said first named I member, said Venturi member having a portion projecting into said mixing conduit, an upper body member mounted above said Venturi member and having an opening forming the upper part of said mixing conduitfand heat insulating 7 having a fuel reservoir and a fuel nozzle therein,-

gaskets separating said Venturi member from said upper andbase members, the wall of said mixing conduit and the outer wall of said projecting portion being spaced apart to prevent direct transference of heat.

5. In combination with an internal combustion engine, a manifold, a carburetor body member said nozzlebeing upwardly inclined and leadin and a downwardly extending idle conduit con- 5 nected tosaid conduit below said vent, a flanged Venturi member mounted between said body member and said manifold, a portion of said flanged member being cut away to interrupt the transfer of heat from said manifold to said body member, and a pair of spaced insulating gaskets inserted between another portion of said Venturi member and said body and said manifold for further interrupting said transfer of heat.

6. A downdraft carburetor having a flangedbase member for attachment to the intake manifold of an engine, a substantially cylindrical mixing conduit in said flanged member, the upper end of said mixing conduit being slightly enlarged, a flanged Venturi member mounted above said first named member and having a venturi projecting into the enlarged portion of said mixing conduit, the enlargement of said mixing conduit forming a clearance between the base member and the venturi, thereby preventing the direct transfer of heat from said lower flanged member to said upper flanged member, and heat insulating gaskets on each side of said flanged Venturi member for interrupting the transfer of heat from the manifold to the carburetor.

'7. A downdraft carburetor comprising upper and lower body members separated by a Venturi member, said Venturi member extending substantially into at least one of said upper and lower body members and having a surrounding flange extending between said upper and lower body members, the extreme ends only of said Venturi member being in substantial contact with said upper and lower body members, and insulating gaskets between said flange and each of said upper and lower body members.

8. A downdraft carburetor comprising upper and lower body members separated by a Venturi member, said Venturi member extending substantially into ,said upper and lower body members and having a surrounding flange extending between said upper and lower body members, the extreme ends only of said Venturi member being in substantial contact with said upperand lower body members, and insulating gaskets between said flange and each of said upper and lower body members.

9. In a structure of the class described, a. carburetor body member having a fuel chamber therein, a part for direct association with an internal combustion engine, a metallic Venturi member having a flange between said body member and said part, and apair of spaced heat in-, sulating gaskets for resisting the direct transfer of heat from said part to said carburetor.

10. In a carburetor, a base member for direct association with the body of an internal combustion engine, there being a conduit in said base member and the upper portion of said conduit I being slightly enlarged, a flanged member mount- 

